1. Field of the Invention
The present invention relates to an optical apparatus having an optical anti-shake function such as a camera, an interchangeable lens, or a telescope, and more particularly to an optical apparatus which realizes the optical anti-shake function using an electro-optic element.
2. Description of the Related Art
In order to reduce an image blur caused by a shake such as a hand shake, previously, an optical anti-shake apparatus which deflects luminous flux heading to an image plane by shifting a lens or changing an apex angle of a variable angle prism has been proposed (see Japanese Patent Laid-open Nos. 2004-61910 and H2-168223). Furthermore, an optical anti-shake apparatus which uses a liquid crystal inclusion element in which a refractive-index variable liquid crystal is included in a wedge-shaped space and a voltage applied to the liquid crystal inclusion element is controlled to uniformly changes the refractive index of the liquid crystal to deflect the luminous flux is proposed (Japanese Patent Laid-open No. H8-152504).
Generally, a frequency range of a hand shake generated by holding an optical apparatus with hands to take or observe an image by a user is around 0.1 to 10 Hz, and the hand shake can be well corrected by the optical anti-shake apparatus disclosed in Japanese Patent Laid-open Nos. 2004-61910 and H2-168223. However, a shake generated in a tripod to which an optical apparatus is attached to take an image or the like sometimes has a frequency of 4 to 35 Hz higher than that of the hand shake. In addition, when the optical apparatus is used on a mobile object such as a vehicle, a shake in a wide frequency range of a few Hz to a few hundreds of Hz is generated.
However, in the optical anti-shake apparatus disclosed in Japanese Patent Laid-open Nos. 2004-61910 and H2-168223, because a mechanical drive of the lens or the variable angle prism is necessary, it is difficult to sufficiently correct the image blur of a frequency beyond the frequency range of the hand shake.
Furthermore, in the optical anti-shake apparatus disclosed in Japanese Patent Laid-open No. H8-152504, because a response speed of the refractive-index variable liquid crystal is around 10 Hz, it is not suitable for the image shake in a high-frequency range of around a few hundreds of Hz. In addition, because the refractive-index variable liquid crystal is included in a wedge-shaped manner, the luminous flux is deflected even if it is not in an anti-shake state. Therefore, in the same optical cross section, an anti-shake state and a non-anti-shake state cannot be switched only by one liquid crystal inclusion element, and a combination of at least two liquid crystal inclusion elements is necessary. As a result, the size of the optical apparatus tends to be enlarged.